A printed circuit board (PCB) is generally flat, and is a multi-layer board made of fibreglass with copper tracks extending between the layers of the board. The PCB includes a plurality of component holes that connect the copper tracks from one layer of the board to other layers of the board. The component holes generally extend from a top surface of the board to a bottom surface of the board. Each component hole is cylindrical and includes a constant diameter therethrough (e.g., from the top surface of the PCB to the bottom surface of the PCB). Each component hole is configured to receive a cylindrically shaped lead of an electronic component (or through-hole electrical component). Each component hole couples the lead to a corresponding track in a corresponding layer of the PCB. Solder is applied to the component hole to fixedly couple the lead of the electronic component to the corresponding track(s) of the PCB and to facilitate electrical communication therethrough.
Traditional vias consist of holes drilled through a PCB 101 as shown in cross section in FIGS. 1A and 1B. The vias may then be plugged as in FIG. 1A or unplugged as in FIG. 1B. Typically, the vias connect one layer of a PCB to another layer, for example, connecting a track 103 to another track 105.
Component leads may also be soldered to vias. In a plugged via, for example, a lead 107 may be soldered to the plugged area 109. The bond formed by the solder, however, may be weakened because of issues of coplanarity, since the lead plane may not be parallel with the PCB (and via) plane. Further, alignment of the leads may be difficult, since the lead must rest atop the via while the soldering is done. Additionally, since there is often limited space available on the surface of the PCB, only a small amount of solder may be applied, which may also lead to a weaker bond. Also, because of concerns about, for example, alignment, the vias must be of a certain size to ensure a high likelihood that the lead will be aligned with the appropriate via once soldered.
Traditional unplugged vias, such as shown in FIG. 1B, may receive larger components with pins 111 designed to be placed through the via 113. Since the pin typically occupies the majority of the space in the via, there is little room for solder to fill the via and create a strong bond. Solder may need to be applied to the side of the PCB opposite the component to ensure a complete bond, often leaving a small pile of solder exposed on the PCB and occupying valuable surface space. Also, soldering irons may have difficulty accessing the pins for soldering on tightly packed boards. Resultantly, wave soldering may need to be used, increasing thermal stress.